The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Internal combustion engines combust an air/fuel (A/F) mixture within cylinders to generate drive torque. The combustion of the A/F mixture produces exhaust gas that may be expelled from the cylinders through an exhaust manifold and an exhaust system. The exhaust system may include components to treat the exhaust gas to reduce emissions. For example, the exhaust gas may include nitrogen oxides (NOx).
Components that treat exhaust gas may include, but are not limited to, external exhaust gas recirculation (EGR) systems, catalytic converters, and selective catalytic reduction (SCR) systems. Furthermore, the exhaust system may include one or more NOx sensors that measure an amount of NOx output by the exhaust system. Thus, the one or more NOx sensors may be used as feedback to adjust engine operation (i.e. engine A/F ratio) and/or exhaust system operation (i.e. percentage of EGR) to reduce the amount of NOx in the exhaust gas.